Protein-corticosteroid interactions in peripheral plasma and synovial fluid of patients with rheumatoid arthritis and osteoarthrosis.

The individual protein fractions, together with the unbound (biologically active) and specifically globulin-bound 11-hydroxysteroids, were determined in the plasma and synovial fluid of patients with rheumatoid arthritis (RA). The values were compared with those measured in control subjects and in patients with severe osteoarthrosis (OA). Hypoalabuminaemia and hyperglobulinaemia, as well as an increase in the unbound and a decrease in the specifically bound corticosteroids were found in the plasma of the RA patients. The protein and corticosteroid levels were lower, and the level of the protein-bound corticosteroid fraction higher, in the synovial fluid than in the plasma. Significant differences between the RA and OA patients in respect of these parameters were also observed. The findings indicate that the altered hormone pattern is not a nonspecific result of the permanent stress situation to which RA patients are subjected. They point out the existence of a fairly specific but still unknown mechanism that compensates the high level of unbound corticosteroids, thus accounting for the absence of any clinical signs of hypercortisonism.